This invention relates to the field of vibration damping and isolation. In particular, the present invention is a damping and isolation system that uses magnetics to cancel the majority of the static stiffness of a viscous fluid, vibration damping and isolation system.
A precision payload, such as a telescope, is susceptible to vehicle disturbances that produce line-of-sight jitter and reduce the optical performance. These disturbances may come from devices such as the reaction wheel assemblies used to point the vehicle. Therefore, an efficient means of damping and isolating, in a controlled manner, either the payload or disturbance source is of considerable importance.
Typically, to minimize performance degradation caused by vibrations, a passive damping and isolation system (otherwise known as a "fluid damper") has been used for damping and isolating the load carried by a precision isolation system. Present passive fluid dampers operate by displacing a viscous fluid from one fluid reservoir to another fluid reservoir through a restrictive passage. Shearing of the viscous fluid as it flows through the restrictive passage provides a damping force that is proportional to velocity.
To function properly, one of the fluid reservoirs must be pressurized with respect to the other fluid reservoir to force the viscous fluid to flow from one reservoir to the other through the restrictive passage. This pressurization must be contained by the fluid damper structure for the fluid damper to operate consistently over its useful life. To prevent leakage of the viscous fluid, hermetic seals, such as bellows, are used. Since the structure of the bellows must be robust enough withstand internal fluid pressures and buckling, the bellows add static stiffness to the damping and isolation system. Though this static stiffness is important to the structural integrity of the damping and isolation system, the static stiffness affects the overall performance of the vibration damper. In particular, while passive fluid dampers provide exceptional vibration damping and isolation at high frequencies (i.e., above the square root of two times resonant frequency) passive dampers amplify disturbances at low frequencies. This amplification of disturbances at low frequencies is due primarily to the static stiffness requirements of the bellows (i.e., flexure components) of the passive fluid dampers. In a three parameter system the amplification can be reduced by increasing the ratio of volumetric stiffness (Kb) to static stiffness (Ka).
There is a need for improved damping and isolation systems. In particular, there is a need for a damping and isolation system that will cancel the majority of the static stiffness of flexure components within the damping and isolation system. In addition, the damping and isolation system should allow more freedom of design of the flexure components, while providing acceptable levels of vibration damping and isolation. The damping and isolation system should provide these features while maintaining a weight, size and complexity efficient structure.